Component and Method of Manufacturing a Component Using an Ultrathin Carrier

ABSTRACT

A system and method for manufacturing a packaged component are disclosed. An embodiment comprises forming a plurality of components on a carrier, the plurality of components being separated from each other by kerf regions on a front side of the carrier and forming a metal pattern on a backside of the carrier, wherein the metal pattern covers the backside of the carrier except over regions corresponding to the kerf regions. The method further comprises generating the component by separating the carrier.

TECHNICAL FIELD

Embodiments of the invention relate generally to a method of manufacturea component, and in particular embodiments, to a method of manufacture acomponent using an ultrathin wafer.

BACKGROUND

Processing ultrathin wafers is difficult because they break easier thanregular wafers during dicing. Moreover, the separated chips may breakduring the pick-up process or while wire bonded.

SUMMARY OF THE INVENTION

In accordance with an embodiment of the present invention, a method formanufacturing a component comprises forming a plurality of components ona carrier, the plurality of components being separated from each otherby kerf regions on a front side of the carrier and forming a metalpattern on a backside of the carrier, wherein the metal pattern coversthe backside of the carrier except over regions corresponding to thekerf regions. The method further comprises generating the component byseparating the carrier.

In accordance with an embodiment of the present invention, a method formanufacturing a component comprises forming a plurality of components ona carrier and forming a metal pattern on a backside of the carrier, themetal pattern comprising free standing metal blocks separated by spaces.The method further comprises forming the component by separating thecarrier along the spaces.

In accordance with an embodiment of the present invention, a method formanufacturing a wafer comprises forming kerf regions and chips on afirst main surface of the wafer and forming a metal pattern on a secondmain surface of the wafer, wherein the metal pattern covers the secondmain surface of the wafer except over regions corresponding to the kerfregions.

In accordance with an embodiment of the present invention, a packagedsemiconductor device comprises a carrier and a component disposed on thecarrier, the component comprising a substrate having a thickness ofabout 20 μm or less and a metal block comprising a thickness of about 20μm or more. The packaged semiconductor device further comprises aconnection layer connecting the carrier and the component, and aconductive wire or a conductive clip connecting a component contact padof the component with a carrier contact pad of the carrier. The packagedsemiconductor device finally comprises an encapsulant encapsulating thecomponent.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 shows a flow chart of an embodiment of a method to manufacture acomponent package;

FIG. 2 shows an embodiment of a top surface of a patterned photoresiston the backside of a carrier;

FIG. 3 a shows an embodiment of a top surface of a patterned metal layeron the backside of a carrier;

FIG. 3 b shows an embodiment of a cross-section of a patterned metallayer on the backside of a carrier;

FIG. 4 shows an embodiment of a singulated component having a metalblock on the backside;

FIG. 5 a shows an embodiment of a packaged component comprising a metalblock on the backside;

FIG. 5 b shows an embodiment of a packaged component comprising a metalblock on the backside;

FIG. 6 a shows an embodiment of a backside metal pattern arrangement;and

FIG. 6 b shows an embodiment of a backside metal pattern arrangement.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the presently preferred embodiments arediscussed in detail below. It should be appreciated, however, that thepresent invention provides many applicable inventive concepts that canbe embodied in a wide variety of specific contexts. The specificembodiments discussed are merely illustrative of specific ways to makeand use the invention, and do not limit the scope of the invention.

The present invention will be described with respect to embodiments in aspecific context, namely a thin wafer processing method and device. Theinvention may also be applied, however, to other carrier processingmethods and devices.

A safe and secure processing of conventional wafers and chips typicallyrequires a silicon thickness of about 60 μm or more for the substrate ofthe wafers or chips. Processing of wafers or chips below this thicknessis difficult because there are serious handling problems in front endand back end processes. For example, when the chips are removed from thesawing foil (pick-up) they may break or fracture due to their thinsilicon substrate. Moreover, when the chips are wire bonded they maybreak or crack due to the mechanical pressure and the ultrasound appliedto the chips. A 100% loss of the processed chips may be experienced.

Embodiments of the invention provide mechanical stabilization ofultra-thin carriers and components. Embodiments of the invention furtherprovide an excellent electrical and thermal contact on the backside of acomponent. Embodiments of the invention provide a void free backsidecontact for a component. An advantage of the mechanical stabilization ofthe component and the carrier is a reliable handling of the componentand the carrier with an ultra-thin substrate. A further advantage ofcomponents with ultra-thin substrate is that the electrical and thermalparameters are improved relative to components with regular sizedsubstrate. For example, the electrical resistance of the components maybe reduced because of the thinner substrate.

FIG. 1 shows a flow chart 100 of an embodiment of a method formanufacturing a packaged electric component. In a first step 110, acarrier is mounted on a support carrier. The carrier may be a workpiece,a substrate, a wafer, or a printed circuit board (PCB).

The carrier may be a semiconductor substrate such as silicon orgermanium, or a compound substrate such as SiGe, GaAs, InP, GaN or SiC.Alternatively, the carrier comprises other materials. The substrate maybe a single crystal silicon or a silicon-on insulator (SOI). Thesubstrate may be doped or un-doped.

One or more interconnect metallization layers may be arranged on thecarrier. A passivation layer is disposed on the interconnectmetallization layers forming a top surface or a first main surface ofthe carrier. The passivation layer may electrical isolate and structurecomponent contacts or component contact pads of the components of thecarrier. The passivation layer may comprise SiN, for example. The firstmain surface is located on the front side of the carrier. The carriercomprises a bottom surface or a second main surface. The second mainsurface is located on the backside of the carrier.

In one embodiment, the first main surface is the surface where theactive areas are predominately disposed and the second main surface isthe surface which is active area free or which is predominately activearea free.

The carrier comprises a plurality of components such as chips or dies.The component may comprise a discrete device such as a singlesemiconductor device or an integrated circuit (IC). For example, thecomponent may comprise a power semiconductor device such as a bipolartransistor, an insulated gate bipolar transistor (IGBT), a power MOSFET,a thyristor or a diode. Alternatively, the component may be resistor, aprotective device, a capacitor, a sensor or a detector, for example.

The carrier comprises kerfs, kerf lines or kerf regions separating andstructuring the components. The carrier is separated, singulated or cutalong the kerf lines into single components. The carrier comprises agrid or a pattern of kerf lines in x-direction and in y-directions. Thekerf lines are the region along which the components are separated fromeach other.

The carrier may be attached to a support carrier. The support carriermay be a glass carrier. Alternatively, the support carrier may besemiconductive carrier such as a silicon carrier. In one embodiment, thefirst main surface of the carrier is glued to the glass carrier so thatthe second main surface of the carrier is exposed.

In step 115, the carrier is thinned, that is, the thickness of thebackside of the carrier is reduced. For example, the substrate isthinned to a thickness of about less than about 40 μm or to a thicknessof about less than about 20 μm. Alternatively, the substrate is thinnedto a thickness of about 10 μm to about 20 μm. The substrate may bethinned by grinding or abrasive cutting. A mercury cleaning whichremoves excess glue residues after mounting the carrier to the supportcarrier may not be carried out because the cleaning step may lead toedge breakings of the component during grinding.

In step 120, the carrier is smoothened and cleaned. For example, thecarrier is smoothened applying a wet etch such as an HNO₃ and a cleanedapplying a water cleaning.

In step 125, an optional stress relaxation is carried out. The stressrelaxation may be advantageous because the substrate thickness (afterthinning) may be in a same or similar dimension range as theinterconnect metallization layers on the front side of the carrier andthe CTEs of the substrate and the interconnect metallization layers aredifferent. The stress relaxation may be carried out applying a Cryoprocess. For example, the Cryo process may be carried out attemperatures of about −70° C.

In step 130, the backside of the carrier is aligned to the front side ofthe carrier. In one embodiment the front side alignment mark is copied,imaged, mapped or reproduced on the backside of the carrier.Alternatively, the backside of the carrier is aligned with the frontside alignment mark. For example, the carrier can be aligned by “seeingthrough” the substrate of the carrier.

In step 135, optionally an under-layer is formed on the backside of thecarrier. The under-layer may be a metal layer. For example, theunder-layer may be aluminum (Al) or aluminum alloy, titanium (Ti) ortitanium alloy, or a combination thereof. Alternatively, the under-layermay comprise copper (Cu), nickel vanadium (NiV) or silver (Ag). Theunder-layer may be a layer stack. For example, the under-layer maycomprise a first layer adjacent to the carrier and a second layerdisposed on the first layer. The first layer may be an adhesion layerand the second layer may be barrier layer. In one example, the firstlayer comprises an aluminum or aluminum alloy (e.g., 200 nm thick) andthe second layer comprises titanium or titanium alloy (e.g., 200 nmthick). The under-layer may be formed by sputtering. Alternatively otherdeposition processes may be used such as physical vapor deposition(PVD), chemical vapor deposition (CVD) or evaporation.

A seed layer is formed over the under-layer. The seed layer may be ametal layer. For example, the seed layer may be aluminum (Al) oraluminum alloy, copper (Cu) or copper alloy, or a combination thereof.The seed layer may be formed by sputtering. Alternatively otherdeposition processes may be used such as physical vapor deposition(PVD), chemical vapor deposition (CVD) or evaporation. In one embodimentsputtering is carried out at low temperatures, e.g., at temperatures ofabout 100° C. In one embodiment the under-layer and the seed layer areformed in a single process forming a layer stack providing a contact, abarrier and a seed layer.

In step 140, a photoresist is formed over the seed layer. Thephotoresist may be formed by spin-coating. The photoresist may be aresists which enables resist thicknesses larger than about 20 μm. Then,in step 145 the photoresist is patterned and developed. In oneembodiment the photoresist is patterned and developed such that thephotoresist pattern mirrors or maps the kerf regions or kerf lines onthe front side of the carrier. The photoresist is removed over thebackside of the components and remains standing over the kerf regions orkerf lines. In one embodiment patterning of the photoresist formsphotoresist ridges, fins or bars. The ridges, fins or bars may comprisethe form of frames or cross-like bars. The ridges, fins or bars maycomprise the form of a circumference of a square or a rectangular.Alternatively, the ridges, fins or bars may comprise other forms. In oneembodiment the removed portions of the photoresist may comprise the formof panels, squares, rectangles, checks, or blocks. Alternatively, theremoved portions of the photoresist may comprise other forms. FIG. 2shows a detail of an embodiment of a photoresist pattern on the backsideof the carrier. Photoresist ridges, fins or bars 210 remain standingwhile the photoresist is removed from the areas 220. In one embodiment,the ridges, fins or bars 210 comprise the same thickness d₁ inx-direction and in y-direction. The carrier may be cleaned to removeunnecessary organic deposits. For example, the carrier may be cleanedwith an O₂ plasma.

In step 150, a metal pattern is formed. In one embodiment the metalpattern or metal layer is formed by galvanic plating. The carrier isimmersed in a metal bath and the metal pattern (metal blocks) areelectro plated from and over the seed layer between the photoresistridges, fins and bars. For example, the carrier is immersed in a copper(Cu) bath. The metal thickness is adjusted by leaving the carrier apredetermined time in the metal bath. For example, the metal thicknessof the copper blocks may be about 20 μm to about 50 μm or about 20 μm toabout 100 μm. The metal blocks may be thicker than the substrate of thecomponents. In one embodiment the metal is thicker than the substratewhen the metal block is not only configured to be an electrical contactbut also configured to be a heat-sink.

An advantage of the electroplating process is that a thick metal patterncan be formed in a comparably short period of time. A further advantageis that the electroplating process provides void free metal blocks andvoid free interface to the component carrier.

FIG. 3 a shows a detail of a top view of an embodiment of a metalpattern or metal layer (e.g., copper) on the backside of the carrier.The metal blocks 320 are spaced apart from each other by the resistridges, bars or fins 310. FIG. 3 b shows a detail of a cross-sectionalview of the metal pattern on the backside of the carrier. The resistridges, fins or bars 310 are placed between the metal blocks 320 over asubstrate 300. A seed layer and/or under-layer may be disposed betweenthe substrate 300 and the resist bars/metal blocks 310, 320.

In an embodiment the metal pattern is formed by other fast depositingprocesses. For example, the metal pattern may be formed by a screenprinting process applying an inkjet printer or stencil printing process.

In step 155, the remaining photoresist layer is removed. For example,the photoresist frame or the photoresist ridges, fins or bars areremoved. The photoresist is removed by organic liquid media.

In step 160, the support carrier and the carrier are placed on a dicingfoil. Then the support carrier is removed from the carrier. In step 165,the components are separated, singulated or cut from the carrier. In oneembodiment the carrier is singulated using a dicing laser. In oneembodiment the carrier is singulated applying a plasma etch using themetal blocks as hard mask. Alternatively the carrier is singulated usinga dicing saw. An embodiment of a detail of a component 410 with abackside metal 420 is shown in FIG. 4. FIG. 4 shows a distance d of arim or gap 430 between the circumference of the component 410 and thecircumference of the backside metal block 420. In one embodiment it isadvantages that the distance d₂ is as small as possible, e.g., betweenabout 5 μm and about 0 μm.

In step 170, the separated individual components are flipped andassembled on a component carrier. The component carrier may be aworkpiece, a substrate, a wafer, or a printed circuit board (PCB). Inone embodiment the component carrier is a leadframe comprising a metalsuch as copper (Cu) or a copper alloy, nickel (Ni) or nickel alloy,silver (Ag) or silver alloys, or a combination thereof.

The component is attached to the component carrier at the componentplacement area. For example, the metal layer or metal block on thebackside of the component is attached to the top surface of thecomponent carrier. In one embodiment the metal layer is bonded to thetop surface of the component carrier using a soldering, eutectic bondingor an epoxy bonding. Alternatively, the second main surface is bonded orglued to the top surface of the carrier using an adhesive tape, a solderpaste or a solder. In one embodiment the connection between thecomponent and the component carrier is an electrical connection.Alternatively, the connection is an insulating barrier.

In step 175, the component is bonded to the component carrier. Forexample, component contacts or component contact pads disposed on a topsurface or first main surface of the component are bonded to componentcarrier contacts or component carrier contact pads of the componentcarrier. The contacts of the component are wire bonded, ball bonded,clip bonded or otherwise bonded to the contacts of the componentcarrier. The wires or conductive clips comprise a metal such as aluminum(Al), copper (Cu), silver (Ag) or gold (Au).

For example, a first component contact disposed on the first mainsurface of the component is electrically connected to a first componentcarrier contact. The component may further comprise a second componentcontact and/or a third component contact on the first main surface.Alternatively, the component may have other contact pad arrangements onits first main surfaces.

At step 180, the component is encapsulated with a molding compound. Inone embodiment the encapsulation material may be a molding compound. Themolding compound may comprise a thermoset material or a thermoplasticmaterial. The molding compound may comprise a coarse grained material.In one embodiment the molding compound may be applied to encapsulate thecomponent and at least portions of the component carrier. Alternatively,the encapsulation material may be a laminate material such as a prepregmaterial.

Optionally, when several of components are placed on the componentcarrier, the encapsulated component/component carrier may be diced intopackaged electric components each comprising a component. For example,the individual packaged electric components are singulated using adicing saw.

FIG. 5 a shows a packaged electric component comprising a component 500having a thickness d₃ and a metal block 540 having a thickness d₄,wherein d₃ is substantially the same as d₄. The metal block (e.g.,copper) 540 may be soldered to the component carrier (e.g., lead frame)590. One or more component contact pads 512 of the component 500 areconnected via wires or conductive clips 514 to one or more componentcarrier contact pads 592 of the component carrier 590.

FIG. 5 b shows a packaged electric component comprising a component 500having a thickness d₅ and a metal block 540 having a thickness d₆,wherein d₆ is substantially larger than d₅. The metal block 540 maycomprise a heat sink. The metal block (e.g., copper) 540 may be solderedto the component carrier (e.g., lead frame) 590. One or more componentcontact pads 512 of the component 500 are connected via wires orconductive clips 514 to one or more component carrier contact pads 592of the component carrier 590.

FIG. 6 a shows the backside metal pattern arrangement 600 in a flippedposition. A wafer 610 is glued or connected to a glass carrier 620. Thewafer 610 is connected to the glass carrier 620 on its front side. Inthis embodiment an alignment mark is arranged on its backside of thewafer 610. A seed layer or a seed layer together with an under-layer 630is disposed directly adjacent to the wafer 610. The seed layer (togetherwith the under-layer) 630 may comprise a metal layer stack. The seedlayer 630 may cover the entire backside of the wafer 610. A metalpattern 640 (e.g., copper) is arranged over the seed layer/under-layeron the backside of the wafer 610. The wafer (e.g., substrate of thewafer) 610 comprises a thickness d₇ and the metal pattern 640 comprisesa thickness d₈. The thickness d₈ is larger than the thickness d₇. Themetal pattern 640 is structured by a resist pattern 650.

FIG. 6 b shows the backside metal pattern arrangement 600 after it isplaced on a dicing foil 660. The resist pattern 650 and the glasscarrier 620 have been removed. FIG. 6 b shows the backside metal patternarrangement 600 wherein the metal blocks 640 are separated by spaces orair gaps 670. The spaces or air gaps 670 are replacing the removedresist pattern 650. As FIG. 6 b shows the wafer 610 is cut with acutting tool 680 in and along the spaces or air gaps 670. The cuttingtool 680 cuts through the wafer 610 and the under-layer/seed layer 630but not through the metal pattern/blocks 640. The cutting tool 680 maybe a dicing laser.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the invention as defined by the appended claims.

Moreover, the scope of the present application is not intended to belimited to the particular embodiments of the process, machine,manufacture, composition of matter, means, methods and steps describedin the specification. As one of ordinary skill in the art will readilyappreciate from the disclosure of the present invention, processes,machines, manufacture, compositions of matter, means, methods, or steps,presently existing or later to be developed, that perform substantiallythe same function or achieve substantially the same result as thecorresponding embodiments described herein may be utilized according tothe present invention. Accordingly, the appended claims are intended toinclude within their scope such processes, machines, manufacture,compositions of matter, means, methods, or steps.

What is claimed is:
 1. A method for manufacturing a component, themethod comprising: forming a plurality of components disposed on acarrier, the plurality of components being separated from each other bykerf regions on a front side of the carrier; forming a metal pattern ona backside of the carrier, wherein the metal pattern covers the backsideof the carrier except over regions corresponding to the kerf regions;and separating the component from the carrier.
 2. The method accordingto claim 1, wherein forming the metal pattern comprises forming a metalseed layer, forming a patterned resist mask, and electro-plating themetal pattern.
 3. The method according to claim 2, further comprisingforming an under-layer between the seed layer and a substrate of thecomponent, wherein the under-layer comprises a metal adhesion layer anda metal barrier layer.
 4. The method according to claim 3, wherein themetal pattern comprises copper (Cu).
 5. The method according to claim 1,wherein a substrate of the component and the metal pattern comprisesabout the same thickness.
 6. The method according to claim 1, wherein asubstrate of the component comprises a thickness of about 20 μm or less,and wherein the metal pattern comprises a thickness of about 20 μm ormore.
 7. The method according to claim 1, wherein separating thecomponent from the carrier comprises laser cutting the carrier along theregions.
 8. A method for manufacturing a component, the methodcomprising: forming a plurality of components on a carrier; forming ametal pattern on a backside of the carrier, the metal pattern comprisingfree standing metal blocks separated by spaces; and separating thecomponent from the carrier along the spaces.
 9. The method according toclaim 8, wherein forming the metal pattern comprises forming a metalseed layer, forming a patterned resist mask, and plating the metalpattern.
 10. The method according to claim 9, further comprising formingan under-layer between the metal seed layer and a substrate of thecomponent, wherein the under-layer comprises a metal layer stack ofaluminum and titanium, and wherein the seed layer comprises the samematerial as the metal pattern.
 11. The method according to claim 10,wherein the substrate of the component comprises a thickness of about 20μm or less, and wherein the metal pattern comprises a thickness of about20 μm or more.
 12. The method according to claim 11, wherein separatingthe component from the carrier comprises laser cutting the carrier. 13.The method according to claim 11, further comprising placing thecomponent on a leadframe, and encapsulating the component and at least aportion of the leadframe.
 14. The method according to claim 13, whereinplacing the component on the leadframe comprises wire bonding or clipbonding the component to the leadframe.
 15. A method of manufacturing awafer, the method comprising: forming kerf regions and chips on a firstmain surface of the wafer; and forming a metal pattern on a second mainsurface of the wafer, wherein the metal pattern covers the second mainsurface of the wafer except over regions corresponding to the kerfregions.
 16. The method according to claim 15, wherein the metal patterncomprises copper (Cu).
 17. The method according to claim 15, forming themetal pattern comprises forming a seed layer over the second mainsurface of the wafer, patterning a photoresist over the seed layer, andforming the metal pattern in a metal bath.
 18. A packaged semiconductordevice comprising: a carrier; a component disposed on the carrier, thecomponent comprising a substrate having a thickness of about 20 μm orless and a metal block comprising a thickness of about 20 μm or more; aconnection layer connecting the carrier and the component; a conductivewire or a conductive clip connecting a component contact pad of thecomponent with a carrier contact pad of the carrier; and an encapsulantencapsulating the component.
 19. The packaged semiconductor deviceaccording to claim 18, wherein the metal block is a copper block. 20.The packaged semiconductor device according to claim 19, wherein theconnection layer is a solder paste.